Suggestions for healthy snacks to put in bentos?

I spend long hours at Uni every day (as many of us do!), and have to bring extra food so that late-afternoon sugar-craving doesn't send me down the hall to the vending machine.

Any suggestions for healthy snacks that people bring in to work in addition to their actual lunch? I tend to stick with the basics of fruit and granola bars, but they really aren't all that filling! :)